Loss of ATRX expression predicts worse prognosis in pulmonary carcinoid tumors

Loss of alpha thalassemia/mental retardation syndrome X-linked (ATRX), a chromatin regulator, is associated with worse prognosis in pancreatic neuroendocrine tumors. We investigated ATRX expression in pulmonary carcinoid tumors (PCT) and its diagnostic and prognostic role in these patients. Resected PCTs (1997-2017) were reviewed. Tumors were staged according to 8th UICC/AJCC system. ATRX nuclear expression was recorded independently by 2 reviewers. A cutoff of ≤5% of nuclear ATRX expression was statistically established as loss of expression. One-hundred-fifteen patients (72 women [63%]; median age of 60.5 years [interquartile range, 50.8-71.5]) harbored 69 (60%) typical and 46 (40%) atypical PCTs. Median tumor size was 2.3 cm (interquartile range, 1.6-3.8 cm). Loss of ATRX expression was associated with atypical PCTs (OR 7.4 [95% CI, 2.6-23, P <. 001]), when adjusted for lymphovascular invasion and perineural invasion. ATRX expression predicted atypical PCT with sensitivity of 37% (95% CI, 24%-52%), specificity of 92% (95% CI, 86%-98%), AUC of 0.62 (95% CI, 0.52-0.72). Loss of ATRX expression was associated with shorter disease-specific survival (HR = 11, 95% CI, 1.8-68, P =. 01), after adjusting for lymphovascular invasion and presence of metastatic disease at time of diagnosis. Interobserver agreement on ATRX expression by two reviewers was substantial (κ = 0.72 [95% CI, 0.60-0.80]). ATRX expression is more commonly lost in atypical than in typical PCT, and is associated with more aggressive tumor characteristics and shorter disease-specific survival.